The shape of the fMRI BOLD response in children and adults changes systematically with age.

We measured the shape of the BOLD response to visual stimulation in subjects between 7 and 61 years of age. We performed two experiments. In the first experiment, at low temporal resolution (TR = 1 s) and with long stimulus periods, we determined activated voxels in each subject. In the second experiment, at high temporal resolution (TR = 294 ms), we measured the response to an impulse stimulus in these voxels. We found that the shape of the time course changes systematically with age. Among the parameters whose age dependence we determined quantitatively, we found the smallest effect for the latency of the leading edge. Therefore, in order to avoid the potential confounds resulting from this effect, it may be appropriate to use the latency of the leading edge or the peak intensity of the BOLD signal, rather than its trailing edge or the area under the signal, as the salient variable in event-related studies that compare groups of different age.